USE OF PYOCIN TO SELECT A HAEMOPHILUS-DUCREYI VARIANT DEFECTIVE IN LIPOOLIGOSACCHARIDE BIOSYNTHESIS

Haemophilus ducreyi, a cause of genital ulcer disease in developing co untries, appears to facilitate the heterosexual transmission of the hu man immunodeficiency virus in Africa. Despite an increase in studies o f this gram-negative human pathogen, little is known about the pathoge nesis of chancroid. Our studies have shown that the lipooligosaccharid es (LOS) of H. ducreyi may play an important role in ulcer formation. Monoclonal antibody and mass spectrometric analyses identified a termi nal trisaccharide present on H. ducreyi LOS that is immunochemically s imilar to human paragloboside. This epitope is present on the LOS of N eisseria gonorrhoeae, and it may be the site of attachment for pyocin lysis. We have used pyocin, produced by Pseudomonas aeruginosa, to sel ect LOS variants with sequential saccharide deletions from N. gonorrho eae. On the basis of the similarities between N. gonorrhoeae and H. du creyi LOS, we employed the same technique to determine if H. ducreyi s trains were susceptible to pyocin lysis. In this study, we report the generation of a pyocin N-resistant H. ducreyi strain which synthesizes a truncated version of the parental LOS. Further studies have shown t hat this H. ducreyi variant has lost the terminal LOS epitope defined by monoclonal antibody 3F11. This report demonstrates that H. ducreyi is sensitive to pyocins and that this technique can be used to generat e H. ducreyi LOS variants. Such variants could be used in comparative studies to relate LOS structure to biologic function in the pathogenes is of chancroid.